Conventionally, a vehicular air conditioner includes a cooling heat exchanger or the like installed in an air conditioning case to regulate a temperature of air blown from an air blower, and a rotary door to switch blow modes in which temperature-regulated air is blown into a compartment (see, for example, Patent Document 1).
The rotary door is stored in the air conditioning case, and includes first and second outer peripheral portions which extend in a circumferential direction centered at a rotation shaft while being arranged side by side in the circumferential direction at an interval. First and second door openings are provided in respective spaces between the first and second outer peripheral portions. The rotary door is configured in such a manner that the first and second outer peripheral portions and the first and second door openings rotate with a rotation of the rotation shaft.
Multiple blowing openings are provided to the air conditioning case along an outer periphery of the rotary door about the rotation shaft. The multiple blowing openings include a defroster blowing opening, a foot blowing opening, and a face blowing opening.
When one of the first and second door openings communicates with one of the multiple blowing openings, an airflow flowing from another of the first and second door openings is blown into a compartment through the one door opening and the one blowing opening communicating with each other.
Accordingly, when the rotary door rotates, the blowing opening which communicates with the door opening is switched. That is, the blowing opening from which an airflow is blown into the compartment switches from one to another among the multiple blowing openings. Accordingly, the blow modes can be switched. By using the rotary door configured as above, a physical size of the air conditioning case and a pressure loss of an airflow can be reduced in comparison with a case where doors are provided to the respective blowing openings.
The vehicular air conditioner of Patent Document 1 using the rotary door to switch the blow modes in the manner described above is capable of reducing a physical size of the air conditioning case and a pressure loss of an airflow. Hence, a level of noise generated when an airflow passes through the air conditioning case can be lowered over a broad range of frequency.
In practice, however, noise at a predetermined frequency, such as wind noise generated when an air flow passes through the cooling heat exchanger and noise generated at the air blower, propagates to the compartment without being attenuated in the air conditioning case in some cases. In other words, a noise level can be lowered over a broad range of frequency by the rotary door whereas noise at a predetermined frequency may possibly become obvious in comparison with noise at other frequencies, in which case noise at the predetermined frequency may give an occupant in the compartment a feeling of strangeness.